I've been running wallpapers I find online through pngout for quite some time now and am thoroughly impressed with the results. I unleash it upon /usr/share/pixmaps/*png yearly as well. How can one not get satisfaction out of making a file smaller and losing nothing in the process? This habit has left me a little shocked with the results I've been gathering. The subjective observation I'm left with is that over 90% of the images I find lying around can be recompressed losslessly with a fairly sizable saving. It should be standard procedure for a publish-once, subscribed-many medium to ensure optimal size to save on bandwidth, but this just isn't happening....
Quickly, pngout is a closed-source png written by Ken Silverman (yep, of Ken's Labyrinths fame) recompressor which pretty much always beats optipng -o7, pngcrush and advpng in terms of filesize.
I don't use browser disk caches so I searched my homedir for a cache of PNGs. It turns out the only place I hadn't unleashed pngout on was my .themes directory. There weren't too many files in there but I only have a few minutes to whip this together so someday I'll post more convincing results, but for the moment here's what I have...
299 files. Before pngout, took 468473 bytes of disk space, after pngout, took 164470 bytes. 304003 bytes saved. (64% savings) If you want to duplicate these tests, here's my terrible sample data. (Compressed paq8o2 tarball)
Multiply every unoptimized png downloaded from the web by every uncached browser hit it receives and realize how big of a deal this is...
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